1. Field of the Invention
The present invention relates to a cellular cushion which is laterally spreadable inwardly or outwardly depending on the space between the ischial tuberosities of a user seated on the cushion. In addition to providing pressure-relieving comfort for the bony prominences of a sitter's pelvis, the cushion also provides enhanced seated stability.
2. Brief Description of the Prior Art
The pelvis serves as the body's center of mass. When a person moves from a standing to a seated position, the pelvis tends to rotate backwardly, causing the lumbar spine to flatten from its natural lordotic (inwardly curved) shape, resulting in increased muscle activity as the body attempts to restore balance. This results in increased fatigue and discomfort for a sitter over time. In addition, a sitter's pelvis has bony prominences such as the ischial tuberosities and coccyx. Pressure on the bony prominences, particularly the ischial tuberosities, leads to discomfort in sitting.
Providing a comfortable cushion in a vehicle is particularly a problem because of vibrational forces involved riding. Known seats for vehicles, such as motorcycles, usually have a supporting base layer, a cushion layer and an exterior cover layer. On long rides, a rider may fatigue and become saddle sore.
For comfort in sitting, a cushion should help sustain the forward tilt of the pelvis and transfer pressure from the skin tissue surrounding the bony prominences to the buttocks and thighs. A cushion should also adapt to the variable spacing between the ischial tuberosities of the two sexes (i.e., the tuberosities of females are usually more widely spaced than the tuberosities of males) and between different members of the same sex. Hence a cushion that feels good to one user may not be comfortable for another.